William recorded the grade-level and instrument of everyone in the middle school School of Rock below.
Seventh Grade Students
Instrument # of Students
Guitar 9
Bass 11
Drums 9
Keyboard 11
Eighth Grade Students
Instrument # of Students
Guitar 3
Bass 3
Drums 8
Keyboard 6
Based on these results, express the probability that a seventh grader chosen at random will play the keyboard as a fraction in simplest form.
The total number of seventh grade students is 40 (9 + 11 + 9 + 11 = 40).
The number of seventh grade students who play the keyboard is 11.
Therefore, the probability that a seventh grader chosen at random will play the keyboard is 11/40.